1. Field of the Invention
The present invention relates to active material powder including an active material and a coating layer attached to a surface of the active material, and a method of producing the same.
2. Description of Related Art
A metal ion secondary battery (for example, a lithium ion secondary battery; hereinafter also referred to as “all-solid-state battery”) including a solid electrolyte layer in which a flame-retardant solid electrolyte is used has advantageous effects in that, for example, a system for securing safety can be easily simplified.
As a technique relating to such an all-solid-state battery, for example,
International Publication WO 2007/004590 discloses a positive electrode active material having a surface coated with a lithium ion-conducting oxide. In addition, International Publication WO 2007/004590 discloses a method of forming a LiNbO3 layer on a surface of a LiCoO2 powder particle, the method including: coating a surface of a LiCoO2 powder particle with alkoxide by spraying an alkoxide solution thereto by using LiCoO2 powder as a fluidized bed in a tumbling fluidized bed granulating-coating machine; hydrolyzing the particle with moisture in air; and firing the particle.
In an active material powder produced using the technique disclosed in International Publication WO 2007/004590 which includes an active material particle and a layer (coating layer) coating a surface of the active material particle, the thickness of the coating layer formed on the surface of the active material particle is uneven. As a result, a lithium ion secondary battery using this active material powder has a problem in that it is difficult to reduce the reaction resistance.